Many devices, such as aircraft, are typically designed to provide a view of the out-the-window scene for at least one operator to operate the device. In the past, a view of the scenery outside the device was provided through passive means, such as a cockpit windshield, or artificial means through sensors and displays.
Synthetic Vision Systems (SVS) present a completely artificial computer-generated view of the external environment to the crewmember(s). SVS displays are typically based on static geographical and cultural data supplemented by dynamic traffic information. Some implementations of SVS use Global Positioning Satellite (GPS) data to register the data base information dynamically to the aircraft's position and altitude. Supplemental sensors may be used to confirm the GPS position data or provide additional data (e.g., other aircraft, weather events, ground equipment). SVS can use both head-up and head-down displays. Displays typically include an artificial out-of-the-window view out the front and to the sides of the aircraft, and/or any number of symbolic and map presentations.
In contrast, Enhanced Vision Systems (EVS) supplement out-the-window vision via the use of camera/sensor imagery superimposed over real-world, or synthetic, imagery. EVS include sensors that can detect and display images of objects that pilots would not normally be able to see when looking through the cockpit window of an aircraft. For example, EVS can present data from sensors that can penetrate low-visibility weather conditions and darkness, such as RADAR or forward-looking infrared (FLIR). The data presented from the sensors is derived from the current environment and not from a computer database. EVS can be used on both head-down and head-up displays. Other features such as navigation enhancements and proactive systems to avoid controlled flight into terrain and runway incursions can also be integrated in EVS.
The development of synthetic and enhanced vision systems requires several different information technologies: (1) camera systems to provide visual imagery; (2) communication technology for transmitting navigation information; (3) databases to provide terrain data for synthetic images and object signatures to support imaging sensors; (4) computer graphics systems to render synthetic images in real time; (5) onboard imaging sensors, such as solid state infrared or imaging RADAR, to provide scene information through darkness and adverse weather; (6) knowledge-based image interpreters to convert sensor images into a symbolic description; and (7) navigation components integrated with a Global Positioning System or suitable navigation system.
Capabilities provided with SV and EV systems are gaining acceptance among aircraft crewmembers. In 1997, the National Aeronautics and Space Administration (NASA), the United States Federal Aviation Administration (FAA), along with several industry, airline, and university participants, began work on NASA's Aviation Safety Program (ASP). One purpose of the ASP is to develop technologies to enhance flight safety and enable consistent gate-to-gate aircraft operations in normal and low visibility conditions. Large format displays filled with high-resolution images and computer graphics are expected to be provided in the crewstation instead of forward-looking cockpit windows. The systems being developed for the ASP use new and existing technologies, such as Global Positioning System signals, terrain databases, and sensors to incorporate data into aircraft cockpit displays. During ASP test flights, the crew flew approaches and landings from an aircraft equipped with a research cockpit and tested the ability to control and land the aircraft relying only on sensor and computer-generated images and symbology. Although the crews provided positive feedback on the capabilities of the system, windowless cockpits are not expected to be certified for use in commercial or general aircraft by the FAA until the year 2007 or beyond.
Currently, the FAA requires aircraft to provide out-the-window viewing capability with specified horizontal and vertical fields of view. In some circumstances, the configuration of aircraft designed for optimum performance at conditions such as supersonic flight can include a long, pointed nose for drag reduction. Additionally, most contemporary supersonic aircraft designs feature a modified delta wing optimized for high-speed flight that results in high angles of attack at lower speeds. The long nose and high angle of attack at low airspeeds impairs the FAA required forward visibility of the flight crew during some phases of operation.
One solution to reduced cockpit out-the-window visibility includes a movable nose cone, such as the droop-nose design of the Concorde aircraft. A mechanical system with actuators allows the crew to move the aircraft nose from a cruise position to a “drooped” position for takeoff, landing, and ground operation. The droop nose configuration requires additional weight and space for the actuator system, and increases the complexity of the aircraft.
Still another solution to enabling the pilot to see outside the airplane during approach and landing is to include cockpit windows at the lower front fuselage of the aircraft, instead of, or in addition to, the traditional location on the upper front fuselage. Such a configuration provides a window for each crewmember to view a limited portion of the runway during landing, as disclosed in U.S. Pat. No. 5,351,898 issued to Michael S. Koehn. Drawbacks associated with the configuration include increased drag due to the opening(s) in the bottom of the nose of the aircraft, and the loss of space in the nose for other aircraft components. Further, the windows provide very narrow horizontal and vertical fields of view that can impair the pilot's depth perception through lack of spatial references.
It is therefore desirable to provide a display system that overcomes the limitations currently associated with display system configurations for aircraft and other devices with reduced out-the-window visibility.